Why does TurboTax Only let me answer yes if I was full time student for College for a year ? But the Irs page says I can can be credit for one semester?

You are asked about your student status in two places; 1. personal info and 2. education expenses.  The first is used to determine eligibility to be someone else's dependent.  The 2nd is for eligibility for a credit or deduction. In neither place does it specify for the whole year.

If you're having a problem,  try deleting your personal  info and re-entering. 

Go through the entire education interview until you reach a screen titled "Your Education Expenses Summary".  Click delete next to the student's name.  You'll then get the "Your Education Expenses Summary" screen again.  Click the "Add a student" button.

Basically, if you were a full time student for *any* *one* *semester* that started during the tax year, then you may qualify to be claimed as a dependent on someone else's tax return if other conditions are also met.